S2-GPP (ESA – 2010/2013)
Sentinel 2 (S2) is the high resolution optical component of the COPERNICUS European Earth Observation programme managed by the European Commission and developed by the European Space Agency. The role of GPP (Ground Processing Prototype) is to act as a reference processor for Sentinel-2 ortho-rectified products (L1C products) throughout the Sentinel-2 mission lifetime.
With its 300km swath, 10m resolution, 13 spectral bands, and 5 day revisit (with 2 satellites S2A and S2B), Sentinel 2 will focus on monitoring vegetation on the Earth. The role of GPP (Ground Processing Prototype) is to support the in orbit test activity, by processing the first reference products during this commissioning phase.
The objective of the GPP is to set a target for the accuracy of radiometric and geometric processing that will then have to be met by the operational processor (S2 IPF – Image Processing Facility).
A consortium composed of ACS, DLR and Magellium built the prototype:
- ACS: system architecture and decommutation of telemetry,
- DLR: overall validation of the system,
- Magellium: radiometric and geometric modules.
Magellium was responsible for all the radiometric and geometric modules in the ground processing chain. These are the core algorithms of the processing chain. These modules rely on a set of well established high resolution optical libraries provided by CNES (French Space Agency), which have been developed and/or used by Magellium in several other optical missions.
A major key for the success of the S2GPP project is the expertise of Magellium in various domains of optical image processing, such as:
- Image compression & decompression : Decompression of telemetry with specific algorithms (decompression module) and JPEG2000 compression of final geo-localized products (JP2K module).
- Radiometric corrections (Radio_S2 module): Equalization, crosstalk correction and Image deconvolution and noise reduction.
- Geometric algorithms : Viewing model elaboration, geo-location methods (Init_loc_prod module), Ground control points extraction and solving of spatio-triangulation system (Geo_S2 module) and Re-sampling methods for final ortho-rectification (Resample_S2 module).
Modules of L1 production chain, from archive product to ortho-rectified and “ready to use” L1C product.